Minimally invasive devices are often employed for medical procedures, including those involving ablation, dilation, and the like. In a particular situation, an ablation procedure may involve creating a series of inter-connecting or otherwise continuous lesions in order to electrically isolate tissue believed to be the source of an arrhythmia. Such lesions may be created using a variety of different energy transmission modalities, such as cryogenic freezing or heating with radiofrequency (“RF”) energy, for example.
Catheters or devices using cryogenic cooling may be used to lower the temperature of tissue, such as cardiac wall tissue, to an extent such that signal generation or conduction temporarily ceases and allows one to map or confirm that the catheter is positioned at a particular lesion or arrhythmia conduction site. Cryocatheters may also operate at lower temperatures for ablation treatment, e.g., to cool the tissue to a level at which freezing destroys the viability of the tissue, and, in the case of cardiac tissue, permanently removes it as a signal generating or signal conducting locus. Electrically driven RF ablation catheters typically include an arrangement of electrodes configured to contact tissue and apply RF energy thereto so that the tissue heats up due to resistive heating, creating an ablation lesion.
Irrespective of the particular ablation modality employed, the treatment goal common to virtually all cardiac or other ablation treatments is to create an effective lesion and/or provide for the desired, controlled destruction of selected tissues. Whether or not a particular treatment is successful may depend greatly on the qualities or characteristics of the lesion, such as its depth, uniformity, location, or the like. For example, for a cardiac arrhythmia, a particular lesion depth may be required to effectively obstruct the unwanted signal transmission through the problematic tissue region.
Existing therapeutic approaches are often limited in their range of operation, which may necessitate lengthy treatment procedures involving many iterations of ablative lesion forming, and re-mapping or checking the quality of lesion or symptomatic presence prior to completing a treatment procedure. Such steps may require an extended amount of time to perform, thus exposing the patient to undesired risk.
Accordingly, there remains a need for medical devices and methods that achieve an extended range of thermal transfer while ablating tissue more effectively and to a greater depth.